1. Field of Invention
The invention, in general, relates to a method for controlling an internal-combustion engine and, in particular, is advantageously, but not exclusively, applied in an internal-combustion engine provided with a turbocharger-supercharging system that is capable of increasing the power developed by the engine by using the enthalpy of the exhaust gases for compressing the air drawn by the engine and, thereby, increase the suction volumetric efficiency.
2. Description of Related Art
A turbocharger-supercharging system includes a turbocharger provided with a turbine (which is arranged along an exhaust conduit to rotate at a high speed under the action of the exhaust gases ejected by the engine) and with a compressor (which is rotated by the turbine and is arranged along the air-feeding conduit for compressing the air drawn by the engine).
When a sudden, quick request of considerable increase of the driving torque or power occurs [i.e., when the driver strongly pushes onto the accelerator pedal (for example, for overtaking)] from a moderate “driving torque” or “power” condition (low rotational speeds and controlled speeds), a quite obvious turbo-lag is usually present. This phenomenon known as “turbo-lag” or “turbo response” represents the tendency of the engines provided with turbocharger to be lacking in power response upon the quick actuation of the accelerator control and is particularly annoying in the case of applications on sport cars in which the turbocharger-supercharging system allows high performance to be achieved.
The turbo-lag is mainly caused by the inertia moment of the rotor that occurs upon a sudden, quick request for a higher driving torque or power and due to the fact that the overall volume of the circuit located downstream of the compressor must increase the pressure therein.
Several solutions have been proposed over the years in an attempt to reduce the turbo-lag and further improve the performance of the engines provided with turbocharger. A variable-geometry turbocharger or a turbocharger including a plurality of turbines in a configuration in series or in parallel, etc. may be used, for example. However, all the solutions known so far are particularly disadvantageous in terms of costs and overall dimensions.
For example, US2007101977 describes a method for controlling an internal-combustion engine including the steps of determining, in operation, a value of the driving torque requested to the internal-combustion engine and determining the first time derivative of the value of the driving torque requested to the internal-combustion engine.
On the other hand, DE10257061 describes a method for controlling an internal-combustion engine including the steps of determining a value of the driving torque requested to the internal-combustion engine through the accelerator-pedal-position signal.
US2006196183 describes a method for controlling an internal-combustion engine including the steps of: determining, in a preliminary adjustment and set-up step, a number of threshold values; determining, in operation, the first time derivative of the value of the driving torque requested to the internal-combustion engine by comparing the signal related to the accelerator-pedal position in two consecutive time instants; comparing the first time derivative of the value of the driving torque requested to the internal-combustion engine with a threshold value; and controlling the internal-combustion engine as a function of the result of the comparison of the first time derivative of the value of the driving torque requested to the internal-combustion engine with the threshold value.
US2008300768 describes a method for controlling an internal-combustion engine in which, through a “manettino” dial, the driver can select the desired driving mode from three possible driving modes, including a “sport driving” mode (which is characterized by a quicker response to the driver's requests on the accelerator pedal). The control method provides for: determining, in a preliminary adjustment and set-up step, a first threshold value; determining, in operation, the first time derivative of the value of the driving torque requested to the internal-combustion engine; comparing the first time derivative of the value of the driving torque requested to the internal-combustion engine with the first threshold value; and controlling the internal-combustion engine as a function of the result of the comparison of the first time derivative of the value of the driving torque requested to the internal-combustion engine with the first threshold value.
However, all the solutions known so far are particularly disadvantageous in terms of costs and overall dimensions and do not allow an optimal management of the internal-combustion engine, especially in cases of a “sport driving” condition. The object of the invention is to provide a method for controlling an internal-combustion engine that is easy and cost-effective to be implemented.